The traditional way of building optical systems has been to make use of discrete optical components such as mirrors, lenses and filters. These components have found extensive use and can be utilized in many types of applications. However, in many situations, particularly with increased emphasis on miniaturization, discrete components are often too bulky and too difficult to interconnect.
Some of these obstacles have been overcome by the development of integrated optics, where all the different optical components are made directly on a substrate. This approach has made it possible to make a large variety of miniature components, but with consequent greatly increased manufacturing complexity and lack of flexibility which does not permit the circuit designer or engineer to rapidly change a design.
The prior art typically employs three dimensional structures for interconnecting optical fibers in predetermined fashions. Examples of such three dimensional structures are found in U.S. Pat. Nos. 4,339,290, 4,498,731 and 4,130,345. In the first patent listed above, and in U.S. Pat. No. 4,483,582, building blocks are employed in optical systems where the adjacent building blocks are aligned by physical contact with each other and not by precise interconnection with a master substrate or equivalent framework.
Several different means of holding optical fibers in predetermined locations are known. Examples of using a polymeric relief pattern are shown in U.S. Pat. Nos. 4,339,290 and 4,164,364. These patterns may be photolithographically created thick film patterns. However, the use of these patterns as shown in the prior art is only for alignment of optical fibers and has no other functions.
The optical systems of the first three patents mentioned above, and U.S. Pat. Nos. 4,306,765 and 4,130,343, disclose semi-reflective or transmissive layers on or in conjunction with optical fiber services. In itself, the use of such layers is well known in optical fiber systems.
One problem with many of the prior art multiple element systems of the type mentioned above is that because the components depend upon accurate surface treatment for proper alignment, errors can be cumulative. In this way, a system so constructed may be very inaccurate in certain aspects of its alignments due to such cumulative errors.